Liquid crystal display having electrodes constituted by a transparent electric conductor

ABSTRACT

A liquid crystal display including: a liquid crystal panel including an array substrate having an upper surface on which a common electrode and a pixel electrode are formed, an opposing substrate disposed so as to be opposite to the upper surface and a liquid crystal layer disposed between the array substrate and the opposing substrate, and a reflecting face. The liquid crystal display is further characterized in that at least one electrode of the common electrode and the pixel electrode is constituted by an electrode portion and a wiring portion, the electrode portion is at least partially constituted by a transparent electric conductor, the electrode portion is formed in a layer separated by an insulating layer from a layer in which the scanning signal line is formed, and the wiring portion is formed in the layer in which the scanning signal line is formed.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/343,464, filed Jun. 17, 2003 now U.S. Pat. No. 7,414,682, which isbased on International Application PCT/JP01/06575 filed Jul. 31, 2001,which claims priority from Japanese Patent Application Nos. JP2000-230449 filed Jul. 31, 2000 and JP 2000-255135 filed Aug. 25, 2000,the contents of which applications are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a liquid crystal display and afabrication method thereof.

BACKGROUND ART

Conventionally, there have been provided IPS (In-Plane-Switching)-mode(transversal electric field type) liquid crystal displays as liquidcrystal displays having a wide viewing angle characteristic. However, inthe IPS-mode liquid crystal display, since a pixel electrode formodulating liquid crystal and a counter electrode are required to belocated relatively close to-one another on one of a pair of substratesretaining the liquid crystal therebetween, a display light incident on aliquid crystal panel is blocked by both electrodes, thereby reducing adisplay light emanating from the liquid crystal panel. Consequently,luminance of a display screen is decreased.

An IPS-mode liquid crystal display for the purpose of addressing thisproblem has been disclosed, for example, in Japanese Laid-Open PatentPublication No. Hei 9-73101. FIG. 25 is a plan view schematicallyshowing a pixel structure of the liquid crystal display. As shown inFIG. 25, in a pixel 402 of the liquid crystal display 401 in a planview, a comb-teeth shaped pixel electrode 403 and a counter electrode404 are disposed so as to oppose to one another, and at least one of thepixel electrode 403 and the counter electrode 404 is constituted by atransparent electric conductor, thereby reducing the amount of displaylight to be blocked by the electrodes 403, 404. Consequently, luminanceof a display screen is increased correspondingly.

However, there is a problem in the liquid crystal display 401 asdescribed below. FIGS. 26 a and 26 b are views schematically showing anoperation of the liquid crystal display 401, wherein FIG. 26 a is asectional view showing an electric field and an alignment of liquidcrystal molecules in a pixel, and FIG. 26 a is a sectional view showinga transmittance distribution in the pixel. In these figures,constitutions of array substrates are simplified for the sake ofillustration. In addition, the pixel electrode 403 and counter electrode404 are here constituted by transparent electric conductors. As shown inFIG. 26 a, the pixel electrode 403 and counter electrode 404 areprovided on the array substrate 411 so as to oppose to one another(juxtaposed to one another) on the plane in which the array substrate411 is present. Therefore, when a voltage is applied across the pixelelectrode 403 and the counter electrode 404, an electric field is formedsuch that both of the electrodes 403, 404 are connected by bow-shapedlines of electric force 406, and liquid crystal molecules 405 arealigned along the lines of electric force. However, in an centralportion of each of the electrodes 403, 404, there is formed a boundaryof the lines of electric force of opposite directions, where liquidcrystal molecules are aligned vertically with respect to the arraysubstrate 411 (hereinafter, simply referred to as vertically) and alongthe lines of electrical force extending toward a point at infinity,thereby forming a liquid crystal disclination area 301. That is, thepixel is divided by the pixel electrodes 403 and the counter electrodes404 into a plurality of domains. As a result, as shown in FIG. 26 b,transmittance 302 of the liquid crystal panel (transmittance in a statein which a voltage is applied in a normally black mode; hereinaftersimply referred to as transmittance) becomes high in an area locatedbetween the electrodes 403, 404 of the liquid crystal where the liquidmolecules 405 are aligned horizontally with respect to the arraysubstrate (hereinafter, referred to as horizontally) because amodulation rate of the liquid crystal molecules 405 becomes large,transmittance 302 becomes low in the disclination area 301 where theliquid molecules 405 are aligned vertically because a modulation rate ofthe liquid crystal molecules 405 becomes small, and transmittance 302becomes medium in an area located above an portion other than thecentral portion of each of the electrodes 403, 404 where the liquidmolecules 405 are aligned obliquely because a modulation rate of theliquid crystal molecules 405 becomes medium. The area 303 where thetransmittance 302 is high, the area 304 where the transmittance 302 ismedium, and the disclination area 301 respectively become a highcontrast area, medium contrast area, and low contrast area. As describedin the foregoing, since a display area includes the low contrast area301, an average contrast of the display screen of the liquid crystaldisplay 401 is reduced.

DISCLOSURE OF THE INVENTION

The present invention has been developed to address the above-describedproblem and an object thereof is to provide a liquid crystal displayhaving a high luminance and a high contrast.

In order to achieve the object, the present invention consists of twoaspects. In a first aspect, portions located below low contrast areas oflight-transmitting electrode and the like are made to belight-non-transmitting portions, thereby improving contrast whilekeeping an effect of improvement of luminance. In a second aspect,reflectance of electrodes and the like is increased, thereby improvingluminance without reducing contrast.

More specifically, a liquid crystal display according to the presentinvention comprises a liquid crystal panel for displaying an image bychanging a transmittance of a display light and one or more structuresdividing a pixel of the liquid crystal panel into a plurality ofdomains, characterized in that at least part of the structure isconstituted by a light-transmitting portion and a light-non-transmittingportion. With this constitution, by locating the light-non-transmittingportion below a boundary portion of the domains formed on the structure,a display light incident on the light-transmitting portion transmitstherethrough, thereby improving luminance of a display screencorrespondingly. On the other hand, since a light incident on thelight-non-transmitting portion does not transmit therethrough, theboundary portion of the domains that is a low contrast area is excludedfrom a display area, thereby improving an average contrast of thedisplay screen correspondingly.

The structure may comprise a light-transmitting layer serving as thelight-transmitting portion and a light-non-transmitting layer serving asthe light-non-transmitting portion formed on inner surfaces of a pair ofsubstrates retaining liquid crystal therebetween in the liquid crystalpanel. In this constitution, the light-transmitting portion and thelight-non-transmitting portion can easily be formed by photolithography.

The structure may divide the pixel into a plurality of domains bycontrolling an alignment of the liquid crystal. In this constitution,the present invention can be applied to a MVA-mode liquid crystaldisplay.

The light-transmitting layer and the light-non-transmitting layer of thestructure may be respectively constituted by a light-transmittingdielectric substance and a light-non-transmitting component. In thisconstitution, luminance and contrast can be improved in the MVA-modeliquid crystal display.

In the above case, the structure may divide the pixel into a pluralityof domains by applying a voltage to the liquid crystal. In thisconstitution, the present invention can be applied to a PVA-mode andtransversal electric field type liquid crystal display.

The light-transmitting layer and the light-non-transmitting layer of thestructure may be respectively constituted by a light-transmittingelectric conductor and a light-non-transmitting electric conductor. Inthis constitution, luminance and contrast can be improved in thePVA-mode and transversal electric field type liquid crystal display.

In the above case, the structure may be formed such that thelight-non-transmitting layer is surrounded by the light-transmittinglayer when seen in a direction perpendicular to the liquid crystalpanel. In this constitution, since a low contrast area is typicallyformed in a central portion of the structure, proper exclusion of thelow contrast portion from the display area enables the contrast to beimproved.

The structure may be formed such that the light-non-transmitting layerand the light-transmitting layer are layered in this order on the innersurfaces of the pair of substrates. In this constitution, since theamount of display light absorbed at the light-transmitting layer isreduced, the amount of recycled light can be increased. Furthermore,with the structure formed by photolithography, a ridge portion is formedon a surface of the light-transmitting layer, and a disclination area isformed above the ridge portion, thereby reliably enabling the contrastto be improved.

The light-non-transmitting layer of the structure may be reflective. Inthis constitution, a light reflected on the light-non-transmitting layeris recycled, thereby enabling the luminance to be improved.

Furthermore, in a liquid crystal display according to the presentinvention, a liquid crystal display of transversal electric field typecomprises a liquid crystal panel in which liquid crystal is retainedbetween a pair of substrates, a plurality of scanning signal lines and aplurality of video signal lines formed so as to define a plurality ofpixels in matrix on an inner surface of one of the pair of substrates,and a pixel electrode and a common electrode formed so as to be alignedin each pixel, wherein an image is displayed on the liquid display panelby inputting a video signal from the video signal line into the pixelelectrode while sequentially selecting the pixel through the scanningsignal line, characterized in that at least one of the scanning signallines, the video signal lines, the pixel electrode, and the commonelectrode is partially constituted by a light-transmitting conductivelayer and a light-non-transmitting conductive layer. In thisconstitution, luminance and contrast can be improved in the transversalelectric field type.

A width of the light-transmitting conductive layer may be narrower thana width of the light-non-transmitting conductive layer.

The width of the light-non-transmitting conductive layer may be narrowerthan the width of the light-transmitting conductive layer by 1 μm ormore. In this constitution, the luminance and the contrast can besuitably improved.

In the above case, the light-non-transmitting conductive layer and thelight-transmitting conductive layer may be layered in this order on theinner surface of the substrate. In this constitution, since the amountof display light absorbed at the light-transmitting conductive layer isreduced, the amount of recycled light can be increased.

An electric conductivity of the light-non-transmitting conductive layermay be higher than an electric conductivity of the light-transmittingconductive layer. In this constitution, since a signal delay is reducedcompared to the case where each of the scanning signal lines, the videosignal lines, the pixel electrode, and the common electrode is entirelyconstituted by a light-transmitting electric conductor, flickering canbe reduced.

The light-non-transmitting conductive layer may be constituted by aplurality of layers having a different reflectance, and a layer closestto the liquid crystal may have a lower reflectance than a layer closestto the substrate. In this constitution, since the amount of ambientlight reflected on a surface of the liquid crystal side thelight-non-transmitting conductive layer is reduced, the contrast can beimproved.

The layer of the light-non-transmitting conductive layer closest to theliquid crystal may be constituted by an electric conductor having ahigher reflectance than aluminum. In this constitution, the amount ofrecycled light is increased, thereby enabling the luminance to beimproved.

A blackening process may be performed on a surface of the liquid crystalside of the light-non-transmitting conductive layer. In thisconstitution, since an ambient light is hardly reflected on a surface ofthe liquid crystal side of the light-non-transmitting conductive layer,the contrast can be suitably improved.

In the above case, a light-blocking layer may be formed on an innersurface of the other one of the pair of substrates so as tosubstantially overlap with the light-non-transmitting conductive layerwhen seen in a direction perpendicular to the liquid crystal panel. Inthis constitution, since an undesired light reflected on a surface ofthe light-non-transmitting conductive layer can be blocked, the contrastcan be improved.

A blackening process may be performed on a surface of the liquid crystalside of the light-non-transmitting conductive layer. In thisconstitution; since an ambient light is hardly reflected on a surface ofthe liquid crystal side of the light-non-transmitting conductive layer,the contrast can be suitably improved.

In a liquid crystal display according to the present invention, a liquidcrystal display of transversal electric field type may comprise a liquidcrystal panel in which liquid crystal is retained between a pair ofsubstrates, a plurality of scanning signal lines and a plurality ofvideo signal lines formed so as to define a plurality of pixels inmatrix on an inner surface of one of the pair of substrates, and a pixelelectrode and a common electrode formed so as to be aligned in eachpixel, wherein an image is displayed on the liquid display panel byinputting a video signal from the video signal line into the pixelelectrode while sequentially selecting the pixel through the scanningsignal line, characterized in that at least one of the scanning signallines, the video signal lines, the pixel electrode, and the commonelectrode are partially constituted by a light-transmitting conductivelayer and a light-non-transmitting conductive layer, and the other ofthe scanning signal lines, the video signal lines, the pixel electrode,and the common electrode, which are not constituted by alight-transmitting conductive layer and a light-non-transmittingconductive layer, have a light diffusive surface. In this constitution,since an ambient light diffused at the light diffusive upper surface canbe used for a display light, a semi-transmittance liquid crystal displaycan be achieved. In addition, with the electrodes and the likeconstituted by a silver Ag-based material, the luminance can be furtherimproved.

A light-blocking layer may be formed on an inner surface of the otherone of the pair of substrates so as to substantially overlap with thescanning signal lines, the video signal lines, the pixel electrode, andthe common electrode that have a light diffusive surface when seen in adirection perpendicular to the liquid crystal panel. In thisconstitution, since an ambient light diffused at the light diffusiveupper surface and passing through an area above the electrodes and thelike having a low modulation ratio can be blocked, the contrast can beimproved.

The light-non-transmitting conductive layer may be constituted by anelectric conductor having a higher reflectance than aluminum. In thisconstitution, the amount of recycled light and hence the luminance canbe improved.

A liquid crystal display according to the present invention comprises anarray substrate on an upper surface of which a common electrode, a pixelelectrode, a scanning signal line, a video signal line, and asemiconductor switching device are formed, an opposing substratedisposed so as to be opposite to the upper surface of the arraysubstrate, a liquid crystal panel having a liquid crystal layer disposedbetween the array substrate and the opposing substrate, and a reflectingface, wherein a light reflected on the reflecting face is transmittedthrough the liquid crystal panel, characterized in that at least oneelectrode of the common electrode and the pixel electrode is constitutedby a electrode portion and a wiring portion, the electrode portion is atleast partially constituted by a transparent electric conductor, theelectrode portion is formed in a layer separated by an insulating layerfrom a layer in which the scanning signal line is formed, and the wiringportion is formed in the layer in which the scanning signal line isformed. In this constitution, since the electrode portion is at leastpartially constituted by a transparent electric conductor, the luminanceis improved. Also, since the electrode portion of the electrode isseparated by the insulating layer from the scanning signal line,short-circuit can be prevented.

The common electrode and the pixel electrode may be both constituted bya wiring portion and a comb-shaped electrode portion, and a width of theelectrode portion at least partially constituted by a transparentelectric conductor may be different from a width of the other part ofthe electrode portion. In this constitution, the width of the electrodeportion constituted by a transparent electric conductor can beincreased, thereby improving light-transmittance of the liquid crystalpanel.

The width of the part of the electrode portion constituted by atransparent electric conductor may be larger than the width of the otherpart of the electrode portion. In this constitution, fabrication by useof photolithography can be simplified without reducing thelight-transmittance of the liquid crystal panel.

In the above case, the common electrode and the pixel electrode may beboth constituted by a wiring portion and a comb-shaped electrodeportion, and widths of both of the common electrode portion and thepixel electrode portion may be such that liquid crystal molecules abovean electrode portion constituted by a transparent electric conductor canbe modulated by an electric field generated between both of theelectrode portions. In this constitution, the light-transmittance can beimproved without changing the driving system.

At least one of a width of each electrode portion of the commonelectrode and the pixel electrode and a spacing between both electrodeportions of the common electrode and the pixel electrode may besubstantially equal to or smaller than a spacing between the arraysubstrate and the opposing substrate. In this constitution, since avertical electric field is generated above the electrode portions, andan electric field strength above the electrode portions is increased,light-transmittance of portions where the electrode portions constitutedby a transparent electric conductor in the liquid crystal panel isimproved. Consequently, a liquid crystal display having a higherluminance can be obtained.

In the above case, a width of each electrode portion of the commonelectrode and the pixel electrode may be 1 μm or more and 10 μm or less.In this constitution, combined with other conditions, liquid crystalmolecules above the electrodes can be suitably modulated.

A liquid crystal display according to the present invention comprises aliquid crystal panel having an array substrate on an upper surface ofwhich a common electrode, a pixel electrode, a scanning signal line, avideo signal line, and a semiconductor switching device are formed, anopposing substrate disposed so as to be opposite to the upper surface ofthe array substrate, a liquid crystal layer disposed between the arraysubstrate and the opposing substrate and a reflecting face formed belowthe liquid crystal panel, wherein a light reflected on the reflectingface is transmitted through the liquid crystal panel, characterized inthat at least one of the common electrode, the pixel electrode, thescanning signal line, the video signal line, and the semiconductorswitching device is at least partially constituted by a high reflectanceelectric conductor having a higher reflectance than aluminum. Generally,a light reflected toward the reflecting face on the common electrode,the pixel electrode, the scanning signal line, the video signal line,and the semiconductor switching device is reflected on the reflectingface and recycled, part of which is transmitted through the liquidcrystal panel, thereby contributing to the improvement of luminance ofthe liquid crystal panel. In this constitution, since at least part ofmembers of the electrodes and the like is constituted by an highreflectance electric conductor having a higher reflectance than acommonly used aluminum, the amount of recycled light is increased by theamount of light reflected by the high reflectance electric conductor.Consequently, the light-transmittance of the liquid crystal panel isimproved, and thereby a liquid crystal display having a high luminancecan be obtained. Furthermore, unlike prior art cases where an entirepart of the electrodes and the like is made to be transparent, thecontrast is not reduced. Accordingly, a liquid crystal display having ahigh luminance and a high contrast can be obtained.

In the above case, the high reflectance electric conductor has a lowerresistivity than aluminum, and at least one of the common electrode, thepixel electrode, the scanning signal line, and the video signal line isconstituted by a single layer of the high reflectance electricconductor. In this constitution, since the high reflectance electricconductor has a lower resistivity than aluminum, members of the commonelectrode and the like can be formed with a single layer, therebyenabling manufacturing cost to be reduced compared to a case where multilayers are formed.

A liquid crystal display according to the present invention comprises aliquid crystal panel in which liquid crystal is retained between a pairof substrates, a plurality of scanning signal lines and a plurality ofvideo signal lines formed so as to define a plurality of pixels inmatrix on an inner surface of one of the pair of substrates, a pixelelectrode formed in each pixel and a common electrode formed on an innersurface of the other one of the pair of substrates, wherein an image isdisplayed on the liquid display panel by inputting a video signal fromthe video signal line into the pixel electrode while sequentiallyselecting the pixel through the scanning signal line, characterized inthat a high reflectance layer having a higher reflectance than aluminumis formed across an insulating layer and below at least one of thescanning signal lines, the video signal lines, and the pixel electrode.In this constitution, the amount of recycled light is increased, andthereby the luminance of the display screen can be improved in a TN-modeliquid crystal display.

A liquid crystal display of transversal electric field type according tothe present invention comprises a liquid crystal panel in which liquidcrystal is retained between a pair of substrates, a plurality ofscanning signal lines and a plurality of video signal lines formed so asto define a plurality of pixels in matrix on an inner surface of one ofthe pair of substrates, and a pixel electrode and a common electrodeformed so as to be aligned in each pixel, wherein an image is displayedon the liquid display panel by inputting a video signal from the videosignal line into the pixel electrode while sequentially selecting thepixel through the scanning signal line, characterized in that a highreflectance layer having a higher reflectance than aluminum is formedbeing separated by an insulating layer from at least one of the scanningsignal lines, the video signal lines, the pixel electrode, and thecommon electrode and therebelow. Also, in this constitution, the amountof recycled light is increased, and thereby the luminance of the displayscreen can be improved in a liquid crystal display of transversalelectric field type.

The high reflectance layer may be formed to have substantially the samewidth as the scanning signal lines, the video signal lines, the pixelelectrode, and the common electrode located above the high reflectancelayer. In this constitution, since an area of the high reflectance layercan be maximized without the reduction of the luminance caused by thehigh reflectance layer appearing to protrude from the scanning signallines and the like, the luminance can be effectively improved.

The high reflectance layer may be formed so as to substantially overlapwith the scanning signal lines, the video signal lines, the pixelelectrode, or the common electrode located above the high reflectancelayer when seen in a direction perpendicular to the liquid crystalpanel. Also, in this constitution, since an area of the high reflectancelayer can be maximized without reducing the luminance caused by the highreflectance layer running off projections of the scanning signal linesand the like, the luminance can be effectively improved.

A liquid crystal display according to the present invention comprises anarray substrate on an upper surface of which a common electrode, a pixelelectrode, a scanning signal line, a video signal line, and asemiconductor switching device are formed, an opposing substratedisposed so as to be opposite to the upper surface of the arraysubstrate, a liquid crystal panel having a liquid crystal layer disposedbetween the array substrate and the opposing substrate, and a reflectingface, wherein a light reflected on the reflecting face is transmittedthrough the liquid crystal panel, characterized in that at least one ofthe common electrode, the pixel electrode, the scanning signal line, thevideo signal line, and the semiconductor switching device has aplurality of layers which are non-transparent and having a differentreflectance, and the plurality of layers are such that a layer closestto the liquid layer has a lower reflectance than a layer closest to thearray substrate. In this constitution, since the amount of ambient lightreflected by members of the common electrode and the like becomesrelatively small compared to the amount of light recycled by the membersof the common electrode and the like, reduction of the contrast due toan undesired light can be prevented.

The layer closest to the array substrate may be constituted by anelectric conductor having a higher reflectance than aluminum. In thisconstitution, since the amount of recycled light is increased comparedto prior art, a liquid crystal display having a high luminance can beobtained, while preventing reduction of the contrast due to an undesiredlight.

In the above case, one of the common electrode and the video signal linemay be provided so as to overlap with one another with an insulatinglayer interposed therebetween when seen in a direction perpendicular tothe array substrate. In this constitution, an aperture ratio of thearray substrate can be increased, thereby achieving a liquid crystaldisplay having a high luminance.

A light-blocking layer may be provided on the substrate on which thepixel electrode is formed. In this constitution, the accuracy ofpositioning of the light-blocking layer is determined by the accuracy ofprinting at a time of manufacturing, thereby suppressing decrease in theaperture ratio due to displacement in bonding the array substrate to theopposing substrate. Consequently, a liquid crystal panel having a highaperture ratio and a high luminance can be achieved.

A color filter may be provided on the substrate on which the pixelelectrode is formed. In this constitution, the accuracy of positioningof color filter is determined by the accuracy of printing at a time ofmanufacturing, thereby suppressing decrease in the aperture ratio due todisplacement in bonding the array substrate to the opposing substrate.Consequently, a liquid crystal panel having a high aperture ratio and ahigh luminance can be achieved.

A portion of the common electrode and a portion of the pixel electrodebetween which a substantially transversal electric field is generatedare respectively formed so as to have at least one bent portion and atleast one bent portion that are bent to conform in shape to one anotherin a pixel. In this constitution, a viewing angle characteristic can befurther improved.

The liquid crystal display may comprise a light-blocking layer, whereinthe video signal line and the light-blocking layer are formed so as tohave bent portions bent to conform in shape to the bent portions of thecommon electrode and the pixel electrode when seen in a directionperpendicular to the array substrate. In this constitution, increase inlight-blocking area can be prevented by bending each of the electrodeportions of the electrodes.

In the above case, the semiconductor switching device may be constitutedby a channel etching type thin film transistor. In this constitution,the insulating layer separating the electrode portions constituted bythe transparent electric conductor from the scanning signal lines isconstituted so as to also play a role as a protection layer for thechannel etching type TFT, thereby enabling manufacturing process to besimplified. Consequently, an optimum constitution can be achieved withrespect to manufacturing process.

The semiconductor switching device may be constituted by a thin filmtransistor using poly-silicon. In this constitution, the semiconductorswitching device can be down-sized, thereby improving the aperture ratioof the array substrate. Consequently, a liquid crystal display having ahigh luminance can be obtained.

The higher reflectance than aluminum may be more than 90%. In thisconstitution, since the high reflectance electric conductor or the highreflectance layer has a higher reflectance than aluminum, a liquidcrystal display having a higher light-transmittance and a higherluminance than prior art can be obtained.

The high reflectance electric conductor or the high reflectance layermay be made of an Ag-based material. In this constitution, since partsof members of the common electrode and the like are constituted by anAg-based electric conductor having a higher reflectance than a commonlyused aluminum, a reflectance of a portion constituted by the Ag-basedelectric conductor is increased, thereby increasing the amount ofrecycled light. Consequently, light-transmittance of the liquid crystalpanel is improved, and thereby a liquid crystal display having a highluminance can be obtained.

The object, as well as other objects, features and advantages of thepresent invention will become more apparent to those skilled in the artfrom the following description of the preferred embodiments taken withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1 b are views showing a pixel structure of a liquidcrystal display according to a first embodiment of the presentinvention, wherein FIG. 1 a is a plan view, and FIG. 1 b is a sectionalview taken in the direction of arrows substantially along line Ib-Ib ofFIG. 1 a;

FIG. 2 is a sectional view showing process steps of a fabrication methodof a liquid crystal panel 101;

FIGS. 3 a and 3 b are views showing an operation of the liquid crystaldisplay of FIGS. 1 a and 1 b, wherein FIG. 3 a is a sectional viewshowing a pixel, and FIG. 3 b is a partially enlarged sectional viewshowing a section of a counter electrode;

FIGS. 4 a and 4 b are views showing a pixel structure of a liquidcrystal display according to a first modification of the firstembodiment of the present invention, wherein FIG. 4 a is a plan view,and FIG. 4 b is a sectional view taken in the direction of arrowssubstantially along line IVb-IVb of FIG. 4 a;

FIGS. 5 a and 5 b are views showing a pixel structure of a liquidcrystal display according to a second modification of the firstembodiment of the present invention, wherein FIG. 5 a is a plan view,and FIG. 5 b is a sectional view taken in the direction of arrowssubstantially along line Vb-Vb of FIG. 5 a;

FIG. 6 is a sectional view showing a transmittance distribution of theliquid crystal display according to the first embodiment of the presentinvention;

FIG. 7 is a sectional view schematically showing a constitution of aliquid crystal display according to a third embodiment of the presentinvention;

FIG. 8 is a sectional view schematically showing a constitution of aliquid crystal display according to a fourth embodiment of the presentinvention;

FIG. 9 is a sectional view schematically showing a constitution of aliquid crystal display according to a fifth embodiment of the presentinvention;

FIG. 10 is a sectional view schematically showing a constitution of aliquid crystal display according to a sixth embodiment of the presentinvention;

FIG. 11 is a sectional view schematically showing a constitution of aliquid crystal display according to a seventh embodiment of the presentinvention;

FIG. 12 is a sectional view schematically showing a constitution of aliquid crystal display according to an eighth embodiment of the presentinvention;

FIGS. 13 a and 13 b are views showing a constitution in a vicinity ofpixel portion of the liquid crystal display of FIGS. 1 a and 1 b,wherein FIG. 13 a is a plan view, and FIG. 13 b is a sectional viewtaken in the direction of arrows substantially along line XIIIb-XIIIb ofFIG. 13 a;

FIG. 14 is a view showing changes in recycled light amount with respectto light reflection numbers when a backlight recycle rate is equal to60%;

FIG. 15 is a view showing changes in recycled light amount with respectto light reflection numbers when the backlight recycle rate is equal to90%;

FIGS. 16 a and 16 b are views showing a constitution in a vicinity ofpixel portion of a liquid crystal display according to a ninthembodiment of the present invention, wherein FIG. 16 a is a plan view,and FIG. 16 b is a sectional view taken in the direction of arrowssubstantially along line XVIb-XVIb of FIG. 16 a;

FIG. 17 is a view explaining a dimensional relationship between a linewidth of an electrode and a cell gap;

FIG. 18 is a sectional view showing a partial constitution of a pixelportion of a liquid crystal display according to a tenth embodiment ofthe present invention;

FIGS. 19 a and 19 b are views showing a constitution in a vicinity ofpixel portion of a liquid crystal display according to an eleventhembodiment of the present invention, wherein FIG. 19 a is a plan view,and FIG. 19 b is a sectional view taken in the direction of arrowssubstantially along line XIXb-XIXb of FIG. 19 a;

FIGS. 20 a and 20 b are views showing a constitution in a vicinity ofpixel portion of a liquid crystal display according to a twelfthembodiment of the present invention, wherein FIG. 20 a is a plan view,and FIG. 20 b is a sectional view taken in the direction of arrowssubstantially along line XXb-XXb of FIG. 20 a;

FIG. 21 is a plan view showing a constitution in a vicinity of pixelportion of a liquid crystal display according to a thirteenth embodimentof the present invention.

FIGS. 22 a and 22 b are views showing a constitution in a vicinity ofpixel portion of a liquid crystal display according to a fourteenthembodiment of the present invention, wherein FIG. 22 a is a plan view,and FIG. 22 b is a sectional view taken in the direction of arrowssubstantially along line XXIIb-XXIIb of FIG. 22 a;

FIG. 23 is a sectional view schematically showing a constitution of aliquid crystal display according to a fifteenth embodiment of thepresent invention;

FIG. 24 is a sectional view schematically showing a constitution of aliquid crystal display according to a sixteenth embodiment of thepresent invention;

FIG. 25 is a plan view schematically showing a constitution of a pixelof a conventional liquid crystal display; and

FIGS. 26 a and 26 b are views showing an operation of the conventionalliquid crystal display, wherein FIG. 26 a is a sectional view showing anelectric field and an alignment of liquid crystal molecules, and FIG. 26b is a sectional view showing a transmittance distribution.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, embodiments of the present invention will be described withreference to accompanying drawings.

FIRST EMBODIMENT

FIGS. 1 a and 1 b are views showing a pixel structure of a liquidcrystal display according to a first embodiment of the presentinvention, wherein FIG. 1 a is a plan view, and FIG. 1 b is a sectionalview taken in the direction of arrows substantially along line Ib-Ib ofFIG. 1 a.

In FIGS. 1 a and 1 b, the liquid crystal display according to the firstembodiment includes a liquid crystal panel 101 having a display screenand a liquid crystal panel driving circuit (not shown) for displaying animage corresponding to a video signal on the display screen bymodulating liquid crystal of the liquid crystal panel 101 in response tothe video signal to change transmittance of a display light. Inaddition, the liquid crystal display is configured to be in a normallyblack mode.

As shown in FIGS. 1 a and 1 b, the liquid crystal display is constitutedsuch that liquid crystal 156 is retained between an opposing substrate155 and an array substrate 157, both of which are opposing to oneanother. The opposing substrate 155 and the array substrate 157 are bothconstituted by a glass substrate. A black matrix (hereinafter, referredto as a light-blocking layer (not shown)), color filter (not shown), andalignment layer are layered on an inner face of the opposing substrate155 in this order. The substrate thus constituted is hereinafterreferred to as an opposing side substrate. A plurality of video signallines 153 which are in parallel with one another and a plurality ofscanning signal lines 154 which are in parallel with one another, whenseen in a plan view, are formed in an inner surface of the arraysubstrate 157 so as to be orthogonal to one another and in matrix. Apixel (a display region) 103 is constituted by a region defined by theplurality of video signal lines 153 and the plurality of scanning signallines 154. A mass of pixels 103 constitutes a display screen (notshown). A horseshoe-shaped pixel electrode 152 and a strip-shapedcounter electrode (a common electrode) 151 are formed in each pixel 103so as to oppose to one another. That is, the pixel electrode 152 and thecounter electrode 151 are formed so as to oppose to one another in acomb-teeth shape. Then, both electrodes 152, 153 are formed so as toextend in parallel with the video signal lines 153. Also, one end of thepixel electrode 152 is connected to the video signal line 153 through asemiconductor switching element 160. The semiconductor switching element160 is constituted by a channel etching type TFT (Thin Film Transistor).On the other hand, the counter electrode 151 is connected to a counterelectrode bus line (a wiring portion) 158. Then, a protection film 164is formed so as to cover a surface of the array substrate 157 in whichthese structures are formed, and further an alignment layer is formed soas to cover the protection film 164 (not shown). Hereinbelow, thesubstrate thus constructed is referred to as an array side substrate.

The counter electrode 151 is constituted by two layers including anon-transparent conductive layer 151A made of a metal having a highreflectance, for example, an Ag—Pd—Cu alloy having a reflectance of 98%in an visible light region and a transparent conductive layer 151Bconstituted by a transparent electric conductor, for example, ITO. Thatis, the counter electrode 151 is constituted such that the elongatedplate-shaped non-transparent conductive layer 151A is formed on thearray substrate 157, and the transparent conductive layer 151B is formedso as to cover a periphery of the non-transparent conductive layer 151A.Thus, in the counter electrode 151, when seen in a plan view, an edgeportion thereof is constituted by the transparent conductive layer 151B,and a central portion thereof is constituted by the non-transparentconductive layer 151A.

Next, a fabrication method for the liquid crystal panel 101 thusconstructed will be described with reference to FIGS. 1 a, 1 b, and FIG.2. FIG. 2 is a sectional view showing process steps of the fabricationmethod of the liquid crystal panel 101.

First of all, a fabrication method of an array side substrate will bedescribed. As shown in FIGS. 1 a, 1 b, and FIG. 2, in order to fabricatethe array side substrate, a thin-film conductive layer made of anAg—Pd—Cu alloy and having a film thickness of approximately 0.1 μm isformed on one main face of a glass substrate 157 serving as an arraysubstrate using a vacuum forming machine.

Then, the scanning signal line 154, non-transparent conductive layer151A of the counter electrode 151, and counter electrode bus line 158are selectively formed by photolithography using a first photomask (FIG.1 a, FIG. 2 a).

The, an ITO (Indium Tin Oxide) film 151′ is formed by sputtering so asto be 0.04-0.2 μm in thickness (approximately 0.1 μm in the presentembodiment) on an entire surface of the glass substrate 157 (FIG. 2 b).

Thereafter, patterning is performed by photolithography using a secondphotomask such that a line width of the ITO film 151′ should cover thenon-transparent conductive layer 151A. In this way, a transparentconductive layer 151B is formed (FIG. 2 c). In the present embodiment,the line width of the transparent conductive layer 151B is configured tobe wider than that of the non-transparent conductive layer 151A by 1 μmor more on one side and 2 μm or more on both sides.

Then, using plasma CVD equipment, three kinds of thin-film layersincluding a silicon nitride SiNx layer to be a gate insulating layer ofTFT 161, an amorphous silicon a-Si layer 162 containing littleimpurities to be a channel of TFT, and an N-type amorphous siliconn⁺a-Si layer 163 are sequentially formed on an entire surface of theglass substrate 157 so as to be respectively 0.3 μm, 0.2 μm, and 0.03 μmin thickness. Thereafter, the amorphous silicon a-Si layer 162 isselectively left on a portion to be the channel of TFT by using a thirdphotomask, thereby forming a channel portion of TFT (FIGS. 2 d, 2 e).

Then, a thin-film 152′ made of an Ag—Pd—Cu alloy is formed by sputteringon an entire surface of the glass substrate 157 so as to beapproximately 0.1 μm in thickness (FIG. 2 f).

Thereafter, patterning is performed by photolithography using a fourthphotomask on the thin-film 152′ made of an Ag—Pd—Cu alloy, therebyselectively forming a video signal line 153 and a pixel electrode 152(FIG. 1 a).

Then, etching is performed on the N-type amorphous silicon n⁺a-Si layer163 such that the N-type amorphous silicon n⁺a-Si layer 163 remains on aportion to be source and drain regions of the TFT. In this way, the TFT160 using the channel etching type amorphous silicon is formed. Itshould be noted that, in the above process, the amorphous silicon a-Silayer 162 and the N-type amorphous silicon n⁺a-Si layer 163 can belaser-annealed to form a poly-silicon p-Si layer and a N-typepoly-silicon n⁺p-Si layer respectively, thereby forming a TFT 160 usingpoly-silicon.

Then, using plasma CVD equipment, a protection film 164 constituted by asilicon nitride layer is deposited. Thereafter, an alignment layer isformed on the protection film 164 (FIG. 2 g).

Finally, although not shown in the figures, for the purpose of supplyingan electric signal to the scanning signal line 154 and the video signalline 153, the silicon nitride layer 164 serving as a passivationinsulating layer on the electrodes is selectively removed in a peripheryportion of the glass substrate 157 using a fifth photomask, therebyexposing terminal electrodes.

Next, a fabrication method for the opposing side substrate will bedescribed. In this case, the light-blocking layer, color filter, andalignment layer are sequentially formed on one main surface of the glasssubstrate 155 serving as the opposing substrate. The light-blockinglayer is formed so as to mask the scanning signal line 154 and videosignal line 153 for light blocking.

Then, a liquid crystal panel 101 is assembled using a predeterminedmethod in such a way that a liquid crystal 156 is retained in a gapbetween the opposing side substrate and the array side substrate.

Then, a liquid crystal panel driving circuit and a backlight are added,thereby completing the fabrication of the liquid crystal display.

Next, operation of the liquid crystal display thus constituted andfabricated will be described. FIGS. 3 a and 3 b are views showing theoperation of the liquid crystal display of FIGS. 1 a and 1 b, whereinFIG. 3 a is a sectional view showing the pixel, and FIG. 3 b is apartially enlarged sectional view showing the counter electrode.

As shown in FIG. 3 a, in the liquid crystal display, when a voltage isapplied across the pixel electrode 152 and the counter electrode 151, anelectric field described in the prior art is formed between the pixelelectrode 152 and the counter electrode 151 in response to the appliedvoltage, and a disclination area 301 is formed in a central portion ofeach of the electrodes 151, 152. Liquid crystal 156 in a pixel 103 isdivided by the disclination area 301 into a plurality of domains 391.However, in the counter electrode 151, when seen in a plan view, an edgeportion-thereof is constituted by the transparent conductive layer 151B,and a central portion thereof is constituted by the non-transparentconductive layer 151A. Therefore, since a display light 801 b which isincident on the transparent conductive layer 151B is transmittedtherethrough, luminance of a display screen is improved correspondingly.On the other hand, since a display light 801 c which is incident on thenon-transparent conductive layer 151A is reflected on thenon-transparent conductive layer 151A and returned back to a backlight,light recycling efficiency of the backlight is improved. In addition,since the disclination area 301 which is a low contrast area locatedabove the non-transparent conductive layer 151A is removed from thedisplay area, an average contrast of the display screen is improvedcorrespondingly.

Furthermore, in the case similar to the present embodiment where thecounter electrode 151 is a two-layer structure in which thenon-transparent conductive layer 151A is covered by the transparentconductive layer 151B and formed by a method of photolithography, aridge portion 501 is formed in an upper face of the outer layer 151B,and a ridge portion 164 a reflecting the ridge portion 501 is alsoformed in a layer (an alignment layer not shown) contacting with theliquid crystal 156. Therefore, a boundary of lines of electric force 406is formed in the ridge portion 164 a, so that the disclination area 301is formed above the ridge portion 164 a. Consequently, the contrast canbe reliably improved since the distination area 301 is reliablypositioned above the non-transparent conductive layer 151A.

Furthermore, since the central portion of the counter electrode 151 isconstituted by the non-transparent conductive layer 151A made of asilver Ag-based material having a high electrical conductivity, signaldelay can be reduced compared to prior art in which the counterelectrode 151 is constituted only by the transparent conductive layermade of ITO having a low electrical conductivity, thereby enablingflickering to be reduced.

Next, an example of modification of the present embodiment will bedescribed. FIGS. 4 a and 4 b are views showing a pixel structure of aliquid crystal display according to a first modification example,wherein FIG. 4 a is a plan view, and FIG. 4 b is a sectional view takenin the direction of arrows substantially along line IVb-IVb of FIG. 4 a.

In the example of the present modification, in addition to the counterelectrode 151, the pixel electrode 152 is also a two-layer structureincluding a non-transparent conductive layer 152A and a transparentconductive layer 152B, thereby enabling luminance and contrast of thedisplay screen to be further improved. It should be noted that, ofcourse, in the pixel electrode 152, similarly to the counter electrode151, the ridge portion 164 a shown in FIG. 3 b is also formed, therebyallowing an effect in which the contrast of the display screen reliablyis improved to be obtained.

FIGS. 5 a and 5 b are views showing a pixel structure of a liquidcrystal display according to a second modification example, wherein FIG.5 a is a plan view, and FIG. 5 b is a sectional view taken in thedirection of arrows substantially along line Vb-Vb of FIG. 5 a.

In the example of the present modification, the pixel electrode 152 is atwo-layer structure including the non-transparent conductive layer 152Aand the transparent conductive layer 152B. Also, in this structure, theluminance and contrast of the display screen can be improved.

Finally, effects of the present embodiment will be summarized for thesake of better clarification. FIG. 6 is a sectional view showing atransmittance distribution of the liquid crystal display according tothe present embodiment.

Referring to FIG. 6, as shown in the examples of three constitution, atleast one of the counter electrode 151 and the pixel electrode 152 ofthe liquid crystal display according to the present embodiment is atwo-layer structure including a non-transparent conductive layer and atransparent conductive layer (FIG. 6 shows the case where both of thecounter electrode 151 and the pixel electrode 152 are of two-layerstructure). In this structure, when a voltage is applied across thecounter electrode 151 and the pixel electrode 152, transmittance 302becomes high in an area 303 located between the electrodes 151, 152 ofliquid crystal, transmittance 302 becomes low in the disclination area301, and transmittance 302 becomes medium in an area 304 located above aportion excluding the central portion of each of the electrodes 151,152. As a result, of the display lights 801, a display light 801 b whichis incident on the area 304 having medium transmittance 302 as well as adisplay light 801 b which is incident on the area 303 having hightransmittance 302 is transmitted through the liquid crystal panel, andtherefore, luminance of the display screen is correspondingly improved.On the other hand, of the display lights 801, a display light 801 cwhich is incident on the disclination area 301 is reflected on thenon-transparent conductive layer 151A, 152A of each of the electrodes151, 152, and thus the disclination area 301 having low transmittance isremoved from the display area. Consequently, an average contrast of thedisplay screen is improved correspondingly.

While, in the examples of the constitutions, an inner portion of thepixel 103, that is, only electrodes located in the display area have atwo-layer structure, the scanning signal line 154, video signal line153, or the like may also have a two-layer structure.

SECOND EMBODIMENT

In the first embodiment, the non-transparent conductive layer and thetransparent conductive layer are formed using different photomasks.However, in the present embodiment, a transparent conductive layer isformed using the same mask as a photomask used to form a non-transparentconductive layer. In particular, in forming the non-transparentconductive layer, a line width of the non-transparent conductive layeris adjusted by over-etching so as to be smaller than a line width of thephotomask in an etching process. Thereafter, in forming the transparentconductive layer, the degree of over-etching is adjusted in the etchingprocess such that a line width of the transparent conductive layer iswider than the line width of the previously made non-transparentconductive layer. The degree of over-etching on the non-transparentconductive layer is the degree to which the line width of thenon-transparent conductive layer becomes 2 μm narrower than the linewidth of the photomask.

With this forming method, an electrode constituted by two layersincluding a non-transparent conductive layer and a transparentconductive layer can be formed without increasing the number ofphotomasks.

THIRD EMBODIMENT

FIG. 7 is a sectional view schematically showing a constitution of aliquid crystal display according to a third embodiment of the presentinvention. In FIG. 7, the same reference numerals as in FIGS. 1 a and 1b denote the same or corresponding elements.

As shown in FIG. 7, in the present embodiment, light-blocking layers 322corresponding to the non-transparent conductive layers 151A, 152A of thecounter electrode 151 and the pixel electrode 152 are formed on theopposing substrate 155. The light-blocking layers 322 are formed so asto overlap with the non-transparent conductive layers 151A, 152A whenseen from a direction vertical to the liquid crystal panel 101. Theother respects are similar to those of the first embodiment.

In this constitution, an ambient light incident from the opposingsubstrate 155 and reflected on the none-transparent conductive layers151A, 152A, that is, an undesired light is reduced, thereby enabling thecontrast of the display screen to be improved.

Furthermore, as an example of modification of the present embodiment, ablackening processed layer 376 may be formed on surfaces of thenon-transparent conductive layers 151A, 152A of the counter electrode151 and the pixel electrode 152, instead of providing the light-blockinglayer 322. The blackening processed layer 376 is formed by forming achromium layer having a low reflectance on the surfaces or by performingplasma treatment after forming a silver Ag-based material on thesurfaces. In this constitution, an incident ambient light from theopposing substrate 155 side is absorbed by the blackening processedlayer 376, thereby reducing an undesired light. Consequently, thecontrast of the display screen can be improved.

FOURTH EMBODIMENT

A fourth embodiment of the present invention exemplifies a constitutionof an IPS-mode semi-transmittance liquid crystal display.

FIG. 8 is a sectional view schematically showing the constitution of theliquid crystal display according to the fourth embodiment. In FIG. 8,the same reference numerals as in FIGS. 1 a and 1 b denote the same orcorresponding elements.

As shown in FIG. 8, in the present embodiment, either one of the counterelectrode 151 and the pixel electrode (the pixel electrode in FIG. 8) isconstituted by the non-transparent electric conductor, an upper face 152a of the electrode 152 constituted by the transparent electric conductoris formed to be light diffusive. The other respects are similar to thoseof the first embodiment.

In this constitution, since an incident ambient light 802 from theopposing substrate side is diffused at the light diffusive upper surface152 a, the diffused light can be used as a display light. Consequently,a semi-transmittance liquid crystal display can be achieved.Furthermore, if materials for the electrodes and the like can beconstituted by silver Ag-based or the like metallic materials having ahigh reflectance, the luminance of the display screen can be improved.

FIFTH EMBODIMENT

FIG. 9 is a sectional view schematically showing a constitution of aliquid crystal display according to a fifth embodiment of the presentinvention. In FIG. 9, the same reference numerals as in FIG. 8 denotethe same or corresponding elements.

As shown in FIG. 9, according to the present embodiment, alight-blocking layer 323 is formed at a position on the opposingsubstrate 155 corresponding to the electrode 152 whose upper surface wasformed to be light diffusive in the liquid crystal display of the fourthembodiment. In this constitution, among lights reflected on the uppersurface 152 a of the electrode 152, an undesired light incident on anobserver's eye through a liquid crystal layer having a low modulationratio and located above the electrode 152 can be reduced, therebyfurther improving the contrast of the display screen.

SIXTH EMBODIMENT

FIG. 10 is a sectional view schematically showing a liquid crystaldisplay according to a sixth embodiment of the present invention.

As shown in FIG. 10, in the present embodiment, the present invention isapplied to a so-called MVA (Multi-domain Vertical Alignment)-mode liquidcrystal display. That is, according to a liquid crystal panel 101 in theliquid crystal display 101 of the present embodiment, transparentelectrodes made of ITO are respectively formed on inner surfaces of anopposing substrate 351 and an array substrate 353 in a pixel, and ribshaving a triangular-shaped section are formed on surfaces of each of thetransparent electrodes so as to protrude alternately from the opposingsubstrate 351 side and the array substrate 353 side. The rib 355 formedon the opposing substrate 351 side is made of dielectric substancesimilarly to prior art. On the other hand, the rib 356 formed in thearray substrate 353 side is constituted by two layers including anon-transparent conductive layer 356A formed on a transparent electrode354 and a transparent dielectric layer 356B formed so as to cover thenon-transparent conductive layer 356A. The non-transparent layer 356 ismade of conductive material having a high reflectance. In the liquidcrystal display thus constituted, liquid crystal molecules 405 areoriented obliquely due to an action of the dielectric substances of theribs 355, 356. As a result, a disclination area 301 is formed in a ridgeportion of the rib 355, 356, and this disclination area is a lowcontrast area having a low transmittance (modulation) similarly to thecase of the IPS-mode. However, in the present embodiment, the rib 356 inthe array substrate 353 side is constituted such that thenon-transparent conductive layer 356A is positioned below the ridge.Therefore, a display light 801 b incident on the transparent dielectriclayer 356B passes through this, thereby correspondingly improving theluminance of the display screen. On the other hand, a display light 801c incident on the non-transparent conductive layer 356A is reflected onthe non-transparent conductive layer 356A and returned back to abacklight, thereby improving light recycling efficiency of the backlightand excluding the disclination area 301 located above thenon-transparent conductive layer 356A from the display area.Consequently, an average contrast of the display screen is improvedcorrespondingly.

It should be noted that the rib 355 on the opposing substrate 351 sidemay be of a two-layer structure including a non-transparent conductivelayer and a transparent dielectric layer.

In addition, although, in the above-mentioned constitution, thenon-transparent layer of the two-layer structure is constituted by anelectric conductor, since the non-transparent layer only needs to have alight reflectance, the non-transparent layer may-be constituted by adielectric substance or a semiconductor having a light reflectance.

SEVENTH EMBODIMENT

FIG. 11 is a sectional view schematically showing a constitution of aliquid crystal display according to a seventh embodiment of the presentinvention.

As shown in FIG. 11, in the seventh embodiment, the present invention isapplied to a so-called PVA (Patterned Vertical Alignment)-mode liquidcrystal display. That is, in a liquid crystal panel 101 of a liquidcrystal display according to the present embodiment, electrodes arerespectively formed on inner surfaces of an opposing substrate 361 andan array substrate 362 so as to protrude alternately from the opposingsubstrate 361 side and the array substrate 362 side in a pixel. Theelectrode 363 formed in the opposing substrate 361 side is constitutedby a transparent electric conductor made of ITO, similarly to prior art.On the other hand, the electrode 364 formed in the array substrate 353side is constituted by two layers including a non-transparent conductivelayer 364A formed on the array substrate 362 and a transparentconductive layer 364B made of ITO formed so as to cover thenon-transparent conductive layer 364A. The non-transparent conductivelayer 364 is made of conductive material having a high reflectance. Inthe liquid crystal display thus constituted, an electric field is formedobliquely between the electrode 363 in the opposing substrate 361 sideand the electrode 364 in the array substrate 362 side, and liquidcrystal molecules 405 are oriented obliquely according to the electricfield. As a result, a disclination area 301 is formed in a centralportion of each electrode 363, 364, and this disclination area 301 is alow contrast area having a low transmittance (modulation), similar tothe case of IPS-mode. However, in the present embodiment, the electrode364 in the array substrate 362 side is constituted such that thenon-transparent conductive layer 364A is positioned in the centralportion. Therefore, a display light 801 b incident on the transparentconductive layer 364B passes through this, thereby correspondinglyimproving the luminance of the display screen. On the other hand, adisplay light 801 c incident on the non-transparent conductive layer364A is reflected on the non-transparent conductive layer 364A andreturned back to a backlight, thereby improving light recyclingefficiency of the backlight and excluding the disclination area 301located above the non-transparent conductive layer 364A from the displayarea. Consequently, an average contrast of the display screen isimproved correspondingly.

It should be noted that the electrode 368 on the opposing substrate 361side may be of a two-layer structure including a non-transparentconductive layer and a transparent dielectric layer.

EIGHTH EMBODIMENT

FIG. 12 is a view schematically showing a constitution of a liquidcrystal display according to an eighth embodiment of the presentinvention. FIGS. 13 a and 13 b are views showing a constitution in thevicinity of a pixel in a liquid crystal display of FIG. 12, wherein FIG.13 a is a plan view, and FIG. 13 b is a sectional view taken in thedirection of arrows substantially along line XIIIb-XIIIb of FIG. 13 a.The direction of the liquid crystal display is defined as shown in FIG.12 for the sake of convenience.

As shown in FIG. 12, the liquid crystal display 100 includes a liquidcrystal panel 101 and a backlight 10, the backlight 10 being disposeddirectly below the liquid crystal panel 101.

As shown in FIG. 12 and FIGS. 13 a and 13 b, in the liquid crystal panel101, an opposing substrate 1B is located so as to be opposite to anupper surface of an array substrate 1A, and liquid crystal is locatedbetween both substrates 1A, 1B. A wiring layer 102 is formed on theupper surface of the array substrate 1A. In addition, an alignment layer9A is formed so as to cover the upper layer of the array substrate 1A onwhich the wiring layer was formed. In addition, a light-blocking layer13 having a grid or stripe shape is formed on a lower surface of theopposing substrate 1B, and a color filter 8 is formed so as to cover thelower surface of the opposing substrate 1B on which the light-blockinglayer 13 was formed. Furthermore, an alignment layer 9B is formed so asto cover a lower layer of the color filter 8. Then, the liquid crystal 2is located between the alignment layer 9A formed on the array substrate1A and the alignment layer 9B formed on the opposing substrate 1B. Inaddition, polarizing films (not shown) are respectively provided on thelower surface of the array substrate 1A and the upper surface of theopposing substrate.

A backlight 10 includes a light guiding plate 10 b, a reflecting plate(reflecting surface) 10 c, and a light source 10 a. The light guidingplate 10 b is provided below the liquid crystal panel 101. A pair oftubular light sources 10 a are provided along a pair of opposing sidefaces of the light guiding plate 10 b. The reflector 10 c is provided soas to cover other side faces and a lower surface of the light guidingplate 10 b. Furthermore, a lamp reflector (not shown) is provided so asto cover a periphery of the light source 10 a excluding a portionthereof facing the light guiding plate 10 b, and a diffusive sheet (notshown) for diffusing light is provided on the upper surface of the lightguiding plate 10 b.

Next, the above-mentioned wiring layer 102 will be described in detail.An electric circuit for changing the alignment of liquid crystal 2(hereinafter, referred to as a liquid crystal operation circuit) isconstituted by a load portion and a power supply portion. The loadportion is constituted by a portion formed within the wiring layer ofthe liquid crystal panel 101, and the power supply portion isconstituted by a so-called liquid crystal panel drive circuit. Theliquid crystal panel drive circuit is not shown. Circuit components(hereinafter, referred to as in-panel liquid crystal operation circuitcomponents) such as a common electrode 3, a pixel electrode 4, and thelike are formed in the wiring layer 102 as the load portion of theliquid crystal operation circuit.

As shown in FIG. 13 a, a common electrode 3, a pixel electrode 4, avideo signal line 5, a scanning signal line 6, and a semiconductorswitching device 7 are formed on the array substrate 1 as the in-panelliquid crystal operation circuit components.

In a plan view, the video signal line 5 and the scanning signal line 6are respectively formed linearly, and a plurality of video signal lines5 and a plurality of scanning signal lines 6 are orthogonal and providedon the array substrate 1A so as to be in matrix. An area defined by thevideo signal lines 5 and the scanning signal lines 6 constitutes a pixel103. In each pixel 103, the common electrode 3 and the pixel electrode 4are both formed to be string-shaped (strip-shaped to be more accurate)and constituted by electrode portions 3 a, 4 a functioning practicallyas an electrode by generating a transversal electric field and wiringportions 3 b, 4 b′, 4 b″ functioning as a wire connecting the electrodeportions with each other and the electrode portions with other in-panelliquid crystal operation circuit components. The common electrode 3, inthe present embodiment, is provided such that three electrode portions 3a having a certain length are bent in a zigzag at certain intervals andextend in an extending direction of the video signal line 5, and thewiring portion 3 b is provided so as to linearly extend in an extendingdirection of the scanning signal line 6, connecting central portions ofeach electrode portion 3 a. The wiring portion 3 b is connected to anearth terminal not shown. The pixel electrode 4 is, in the presentembodiment, provided such that two electrode portions 4 a extend in anextending direction of the video signal line 5 and between the threeelectrode portions 3 a of the common electrode 3 so as to be bent in azigzag and so as to conform in shape to the electrode portions 3 a ofthe common electrode 3. The electrode portions 4 a of the pixelelectrode 4 and the electrode portions 3 a of the common electrode 3 areevenly spaced with each other. One ends of the electrode portions 4 aare connected by means of the wiring portion 4 b′ located on thescanning signal line 6, and the other end of one electrode portion 4 ais connected to the semiconductor switching device 7 by means of theL-shaped wiring portion 4 b″. The semiconductor switching device 7 isprovided in the vicinity of an intersection of the video signal line 5and the scanning signal line 6 for each pixel. The semiconductorswitching device 7 is constituted by a well-known TFT, a gate electrodeis connected to the scanning signal line 6, a source is connected to thevideo signal line 5, and a drain is connected to the wiring portion 4 b″of the pixel electrode 4.

Additionally, the wiring layer 102 is, in a sectional view, formed onthe array substrate 1 by layering the common electrode 3 and thescanning signal line 6, the insulating layer (not shown), and the pixelelectrode 4, and the video signal line 5 in this order and from thebottom up. It should be noted that FIG. 13 b illustrates the commonelectrode 3 and the pixel electrode 4 as being in the same layer for thesake of simple description.

Next, materials will be described. The array substrate 1A and theopposing substrate 1B are made of transparent glass. The alignment layer9A, 9B is made of material capable of aligning molecules of the liquidcrystal 2 such as polyimide. The semiconductor switching device 7 ismade of amorphous silicon a-Si used for an active semiconductor layer.

The common electrode 3, the pixel electrode 4, the video signal line 5,and the scanning signal line 6 are made of Ag-based metallic materialshaving a high reflectance of substantially 95% or more in the visiblelight region (hereinafter, referred to as high reflectance metallicmaterials). Of such metallic materials, an Ag—Pd—Cu alloy is preferablein consideration of etching performance and reliability required forpatterning in photolithography. Since Ag-based metallic materials have alow electric resistivity, the use of an Ag—Pd—Cu alloy enables thein-panel liquid crystal operation circuit components to be constitutedby a single layer, thereby reducing the manufacturing cost in comparisonwith the use of multi-layers of Al-based, Cr-based, etc. metallicmaterials. Furthermore, owing to the low electric resistivity, a layerthickness of the in-panel liquid crystal operation circuit componentscan be reduced, thereby enabling the alignment to be reliably formed.Consequently, a liquid crystal display having high picture qualitiessuch as high contrast and low uneven luminance can be achieved. In thepresent embodiment, an Ag—Pd—Cu alloy is used as a high reflectancemetallic material. The composition ratio is Ag:Pd:Cu=0.981:0.009:0.010.

Next, a fabrication method for the liquid crystal display thusconstituted will be described. In FIGS. 12 and 13, first of all, aconductive layer made of high reflectance metallic material is formed onan array substrate 1A, and a common electrode 3 and a scanning electrodeline 6 are formed by patterning the conductive layer. Then, aninsulating layer (not shown) is formed so as to cover a surface of thecommon electrode 3 and the scanning electrode line 6. Thereafter, asemiconductor switching device 7 is formed of amorphous silicon a-Si orthe like, a conductive layer made of high reflectance metallic materialis formed, and a pixel electrode 4 and a video signal line 5 are formedby patterning the conductive layer.

Then, an alignment layer 9A made of polyimide is formed on a surface ofthe array substrate 1 on which the pixel electrode 4 and the videosignal line 5 were formed.

On the other hand, a light-blocking layer 102 and a color filter 8 aresequentially formed on an opposing substrate 1B. In the color filter 8,color filter materials of R (red), G (green), and B (blue) are arrangedin a predetermined pattern. Then, an alignment layer 9B made ofpolyimide is formed on a surface of the opposing substrate 1B on whichthe color filter 8 was formed.

Then, initial alignments are respectively developed in predetermineddirections in the array substrate 1A and the opposing substrate 1B thusconstructed. Then, peripheral portions of-the array substrate 1A and theopposing substrate 1B are bonded together using a sealing agent, andthereafter a space formed between both substrates is filled with liquidcrystal 2 and then sealed, thus completing a liquid crystal panel 101.Thereafter, a backlight 10 is mounted to the liquid crystal panel 101.

Next, operation of the liquid crystal display 100 thus constituted willbe described. In FIG. 13, the semiconductor switching device 7 iscontrolled for on/off according to a driving signal inputted through thevideo signal line 5 and the scanning signal line 6. Then, a voltage isapplied across the pixel electrode 4 and the common electrode 3depending on the control state of the semiconductor switching device 7,thereby causing a transversal electric field to be generated. Thealignment of the liquid crystal 2 varies according to the generatedtransversal electric field, and transmittance of an incident light fromthe backlight 10 varies according to the variation, thereby controllingthe luminance of each pixel 103 for an image display.

By the way, generally, in a display method using an IPS-mode, since thecommon electrode 3 and the pixel electrode 4 are formed to be lined upside-by-side on the array substrate 1A, an aperture ratio of the arraysubstrate 1A is reduced to 30-40%. On the other hand, a light emanatingfrom the light source 10 a of the backlight 10 is repeatedly reflectedon the reflector 10 c and the like and reaches to the array substrate 1Athrough the light guiding plate 10 b. Only part of the light istransmitted through an aperture of the array substrate 1A, that is,through a portion of the array substrate 1A where the in-panel liquidcrystal operation circuit components such as the common electrode 3, thepixel electrode 4, and the like are not formed. However, the other partof the light, after reflected on the in-panel liquid crystal operationcircuit components, is repeatedly reflected within the backlight 10 andthe array substrate 1A, during which part of the other part of the lightis sequentially transmitted through the aperture. That is, even lightunable to be transmitted through the aperture of the array substrate 1Ais recycled when reflected toward the reflecting plate 10 c, and part ofthe recycled light is transmitted through the aperture, therebycontributing to improvement of the luminance of the liquid crystal panel101.

In FIG. 13 b, dashed lines having arrows show a light tracking viewillustrating a state in which a light emanating from the light source 10a is reflected on the reflecting plate 10 c, traveling toward the arraysubstrate 1A, then reflected on the common electrode 3 and the pixelelectrode 4, thereafter returning back to the backlight 10, reflectedagain on the reflecting plate 10 c, then further traveling toward thearray substrate 1A, and finally transmitted through the aperture. Alight transmitted through the aperture of the array substrate 1A afterrepeatedly reflected in the manner described above is defined as arecycled light. Therefore, the amount of recycled light increases ordecreases depending on the reflectance of each component constitutingthe liquid crystal panel 101 and backlight 10, the transmittance of theliquid crystal panel 101, and the number of reflections.

In a conventional liquid crystal display, metallic materials for use inthe in-panel liquid crystal operation circuit components have hardlybeen selected in view of these respects. Rather, in view of cost, oretching performance, reliability, or the like, Cr-based or Al-basedalloys, or a multi-layer wiring formed by combining these alloys withmetal such as Ti, Zr, Mo, or the like has been frequently used.

However, these metallic materials do not have a high reflectance, and,especially, a Cr-based alloy has a low reflectance of approximately 60%.Therefore, a light emanating from the light source 10 a of the backlight10 loses a large amount of light by being repeatedly reflected on thein-panel liquid crystal operation circuit components. Accordingly, theamount of light to be used as a recycled light is small, and therecycled light could hardly contribute to the improvement of theluminance. Therefore, in a conventional IPS-mode liquid crystal display,decrease in aperture ratio of the array substrate directly lead to thereduction of the luminance of the liquid crystal panel, thereby makingthe screen dark.

In contrast, the present invention pays attention to the fact thatrecycled light contributes to the improvement of the luminance. In theliquid crystal display according to the present embodiment, metallicmaterials having a high reflectance are used as materials for in-panelliquid crystal operation circuit components. Accordingly, since theamount of light to be lost while a light emanating from a light source10 a of the backlight is repeatedly reflected between the backlight 10side and the array substrate 1A side or within the liquid crystal panel101 can be reduced, the amount of light that can be used as recycledlight is increased, thereby enabling the recycled light to contribute tothe improvement of the luminance. Consequently, a liquid crystal displayhaving a high luminance can be obtained. In addition, differently fromprior art, where the entire part of the electrodes was made transparent,the reduction of the contrast is not brought about. Consequently, aliquid crystal display having a high luminance and a high contrast canbe achieved.

By the way, the backlight 10 is actually constituted by a diffusivesheet, a collecting prism, a polarization conversion film, and the like,as well as the light source 10 a, the light guiding plate 10 b, and thereflector 10 c and thus very complicated. And, this constitution alsodepends on the model. For the purpose of analyzing the influence ofreflectance of the common electrode 3 and the pixel electrode 4, twokinds of backlights having different constitutions are selected, and forthe two kinds of backlights, a rate (hereinafter, referred to as arecycling rate) was actually measured between the amount of lightreturned to the backlight 10 side and the amount of light returned tothe backlight 10 side, reflected, and again incident on the liquidcrystal panel 101. As a result, the recycling rates of the two kinds ofbacklights were different and approximately 60% and 90%, respectively.Hereinbelow, by comparing these two backlights, influences ofreflectance of the common electrode 3 and the pixel electrode 4(hereinafter, simply referred to as electrodes) on the amount ofrecycled light are examined. Here, the amount of recycled light isrepresented as a rate expressed in % of the amount of light emanatingfrom the light source 10 a of the backlight 10 to the amount of lighttransmitted through the array substrate 1A.

FIG. 14 is a view showing change in the amount of recycled light withrespect to the number of light reflections in the case where therecycling rate of the backlight is 60%. In FIG. 14, reflectance of anelectrode is a parameter, and the relationship between the number oflight reflections and the amount of recycled light is shown in the casewhere the reflectance of the electrode is 60%, 70%, 80%, 90%, or 98%.FIG. 14 shows that when the reflectance of the electrode is increased,the amount of recycled light is increases irrespective of the number ofreflections. For example, when the light reflectance is changed from 60%to 98%, increase in the amount of recycled light is approximately 5% (5points) of the increase when the number of reflections is 5.

FIG. 15 is a view showing change in the amount of recycled light withrespect to the number of light reflections in the case where therecycling rate of the backlight is 90%. Similarly to FIG. 14, in FIG.15, the relationship between the number of light reflections and theamount of recycled light is also shown in the case where the reflectanceof the electrode is 60%, 70%, 80%, 90%, or 98%. FIG. 15 shows that whenthe light reflectance is changed from 60% to 98%, increase in the amountof recycled light is 50% (50 points) of the increase when the number ofreflections is 5 and 30% (30 points) of the increase when the number ofreflections is 10. Accordingly, increase in the amount of recycled lightwith respect to increase in reflectance of an electrode is very large,compared to the case in FIG. 14. Furthermore, when the reflectance of anelectrode is changed from 90% to 30%, increase in the amount of recycledlight is approximately 20% (20 points) of the increase when the numberof reflections is either 5 or 10.

Application of the above-mentioned results to actual electrode materialsshows that since the reflectance of Cr-based metallic material isapproximately 60%, and the reflectance of Ag-based metallic material isapproximately 98%, change of the electrode material from Cr-based toAg-based will increase the amount of recycled light and thereby improvethe luminance. Especially, when the recycling rate of the backlight islarge, even small change in the reflectance of electrode from 90% to98%, that is, change of the electrode material from Al-based toAg-based, will improve the luminance greatly.

In addition, in the present invention, since each electrode portion 3 a,4 a of the common electrode 3 and the pixel electrode 4 is bent,molecules of the liquid crystal 2 are rotated in two directions.Therefore, colors of the liquid crystal pane 101 are offset with respectto each other in the case when the liquid crystal panel is seen from atilted angle, thereby achieving a liquid crystal panel 101 having lesscolor variation irrespective of viewing directions. Consequently, aliquid crystal display having a wide viewing angle can be achieved.

Furthermore, while each one of the in-panel liquid crystal operationcircuit components is entirely made of metallic materials having a highreflectance in the present embodiment, some of the in-panel liquidcrystal operation circuit components may be made of metallic materialshaving a high reflectance, or a certain one of the in-panel liquidcrystal operation circuit component may be partially made of metallicmaterial having a high reflectance.

NINTH EMBODIMENT

A ninth embodiment of the present invention exemplifies a liquid crystaldisplay having a common electrode constituted by a transparent electricconductor among liquid crystal displays in which at least either one ofa common electrode and a pixel electrode is constituted by a transparentelectric conductor.

FIGS. 16 a and 16 b are views showing a constitution in the vicinity ofa pixel portion of a liquid crystal display according to the presentinvention, wherein FIG. 16 a is a plan view, and FIG. 16 b is asectional view taken in the direction of arrows substantially along lineXVIb-XVIb of FIG. 16 a. In FIGS. 16 a and 16 b, the same referencenumerals as in FIG. 13 denote the same or corresponding elements.

According to the present embodiment, differently from the eighthembodiment, the electrode portion 3 a of the common electrode 3 isconstituted by the transparent electric conductor, and the wiringportion 3 b is made of metallic material having a high reflectance, asshown in FIG. 16. The electrode portion 3 a and the wiring portion 3 bare separated by an insulating layer (a second insulating layer 11 and afirst insulating layer not shown), and the electrode portion 3 a and thewiring portion 3 b are connected through a contact hole 11 a provided inthe insulating layer. That is, when seen in a sectional view, the wiringlayer 102 is formed on the array substrate 1 by layering the wiringportion 3 b of the common electrode and the scanning signal line 6, thefirst insulating layer (shown by reference numeral 14 in FIG. 19 b), thepixel electrode 4 and the video signal line 5, the second insulatinglayer 11, and the electrode portion 3 a of the common electrode in thisorder and from the bottom up. It should be noted that the firstinsulating layer is not shown in FIG. 16 b for the sake of simpledescription. The other respects are similar to those of the eighthembodiment.

Next, a fabrication method of the liquid crystal display thusconstituted will be described with reference to FIGS. 16 a and 16 b.

FIGS. 16 a and 16 b, first of all, a conductive layer made of highreflectance metallic material is formed on the array substrate 1A, andthen patterning is performed on the conductive layer so as to form apredetermined shape, thus forming the wiring portion 3 b of the commonelectrode 3 and the scanning signal line 6. The first insulating layer(not shown) is formed so as to cover a surface of the common electrode 3and the scanning signal line 6. Then, a semiconductor switching device 7constituted by an a-Si layer and a n⁺-type a-Si layer (both are notshown) is formed on a predetermined portion of the first insulatinglayer. Furthermore, a conductive layer made of metallic material havinga high reflectance is formed on a portion of the first insulating layerwhere the semiconductor switching device 7 was formed and on apredetermined portion of the semiconductor switching device 7.Patterning is performed on the conductive layer to form a predeterminedshape, thus forming the video signal line 5 and the pixel electrode 4.

Then, a second insulating layer 11 made of SiNx or the like is formed ona surface of the array substrate 1A in which the video signal line 5 andthe pixel electrode 4 were thus formed. The second insulating layer 11also plays a role as a protection film for protecting the semiconductorswitching device 7.

Then, a transparent conductive layer made of ITO is formed on the secondinsulating layer 11, and patterning is performed to form a predeterminedshape, thus forming the electrode portion 3 a of the common electrode.

Here, contact holes 11 a (see FIG. 19 b) are respectively provided inthe first insulating layer and the second insulating layer 11 to achievean electric conduction between the wiring portion 3 b of the commonelectrode made of metallic material having a high reflectance and threeelectrode portions 3 a of the common electrode constituted by thetransparent electric conductor.

Thereafter, the liquid crystal display is attained through the sameprocess steps as in the eighth embodiment.

In the liquid crystal display thus constituted, since the electrodeportion 3 a of the common electrode 3 is constituted by the transparentelectric conductor, the aperture ratio of the array substrate 1A isincreased.

However, electric field intensities in areas above the electrode portion3 a of the common electrode 3 and an electrode portion 4 a of the pixelelectrode 4 are smaller than an electric field intensity in an areapositioned between the electrode portion 3 a of the common electrode 3and the electrode portion 4 a of the pixel electrode 4. Therefore, inorder to substantially increase the aperture ratio of the arraysubstrate 1A, the electrode portion 3 a of the common electrode 3 is notonly constituted by the transparent electric conductor, but molecules ofthe liquid crystal 2 positioned above the electrode portion 3 a of thecommon electrode 3 also need to be reliably modulated (alignment ischanged).

Hereinbelow, the conditions under which the molecules of the liquidcrystal 2 positioned above the electrode portion 3 a of the commonelectrode 3 could be modulated by an electric field generated betweenthe electrode portion 3 a of the common electrode 3 and the electrodeportion 4 a of the pixel electrode 4 will be described. These conditionsare requirements on a line width of an electrode, spacing betweenelectrodes, a cell gap, and a liquid crystal material.

FIG. 17 is a view explaining the relationship between a line width of anelectrode and a dimension of a cell gap, which is a sectional viewshowing the same portion as in FIG. 16 b.

In FIG. 17, d represents a cell gap, w1 represents a line width of theelectrode portion 3 a of the common electrode, w2 represents a linewidth of the electrode portion 4 a of the pixel electrode, and Lrepresents spacing between the electrode portion 3 a of the commonelectrode and the electrode portion 4 a of the pixel electrode. In thepresent embodiment, the line width of the electrode portion 3 a of thecommon electrode w1 is equal to 5˜m, the line width of the electrodeportion 4 a of the pixel electrode w2 is equal to 4˜tm, and the spacingbetween the electrodes L is equal to 10˜tm. That is, each of the linewidths w1, w2 of the electrode portions 3 a˜4 a of the common electrode3 and the pixel electrode 4 is structured to be substantially equal tothe spacing (cell gap) d between the array substrate 1A and the opposingsubstrate 1B. Here, since the electrode portion 3 a of the commonelectrode is constituted by the transparent electric conductor, the linewidth w1 thereof may be thicker than the line width w2 of the electrodeportion 4 a of the pixel electrode constituted by the transparentelectric conductor.

Furthermore, a cyanide-based liquid crystal material havingapproximately 10% or 20% of cyanide-based chemical compound is used as amaterial for the liquid crystal 2, and a retardation Δn·d (product ofcell gap d and refractive index difference Δn) is set to approximately350 nm. In addition, the material for the liquid crystal 2 has a sprayelastic constant K11 of 12 (pN), a twist elastic constant K22 of 7 (pN),a bend elastic constant K33 of 18 (pN), and a dielectric constantanisotropy Δ ∈ of +8. Here, the dielectric constant anisotropy Δ ∈ andthe bend elastic constant K33 are important to determine a drivingvoltage for the liquid crystal. In particular, preferably, thedielectric constant anisotropy Δ ∈ is +8 or more, and the bend elasticconstant K33 is 18 (pN) or less.

Combining the spacing L of the electrodes, the line widths w1, w2 of theelectrodes, and the cell gap d as described above with the liquidcrystal 2 thus constituted enables the electric field strength above theelectrode portions of the electrodes to be sufficiently increased with acommonly used driving voltage (approximately 5 V), thereby allowingmolecules of the liquid crystal 2 positioned above the electrodeportions of the electrodes to be modulated to drive the liquid crystal2. In this way, the molecules of the liquid crystal 2 positioned abovethe electrode portions of the electrodes are reliably modulated.Thereby, in cooperation with the electrode portion 3 a of the commonelectrode constituted by the transparent electric conductor, theaperture ratio of the array substrate 1A is substantially increased.Consequently, the luminance of the liquid crystal display is improved.

Furthermore, when the spacing L between the electrode portions of theelectrodes or the line widths w1, w2 of the electrode portions of theelectrodes is grater than the cell gap d, only a transversal electricfield is generated. However, when the spacing L between the electrodeportions of the electrodes or the line widths w1, w2 of the electrodeportions of the electrodes is equal to or smaller than the cell gap d,not only a transversal electric field is generated, but a verticalelectric field due to peripheral electric fields of the electrodes isalso generated. For example, when the spacing L between the electrodeportions of the electrodes is equal to 3 μm, the line widths w1 and w2are equal to 4 μm, and the cell gap d is equal to 5 μm, not only atransversal electric field but also a vertical electric field aregenerated, thereby increasing the electric field strength above theelectrode portions of the electrodes. Consequently, a high transmittanceis achieved. Therefore, the spacing L between the electrode portions ofthe electrodes and the line widths w1, w2 of the electrode portions ofthe electrodes are preferably smaller than the cell gap d.

Furthermore, line widths of the electrode portion 3 a of the commonelectrode and the electrode portion 4 a of the pixel electrode arepreferably 1 μm or more and 10 μm or less in consideration offabrication conditions in addition to modulation conditions for themolecules of the liquid crystal 2.

It should be noted that, of course, in the present embodiment, since thein-panel liquid crystal operation circuit components excluding theelectrode portion 3 a of the common electrode are made of metallicmaterial having a high reflectance, the effect of improving theluminance by recycled light could be obtained, similarly to the eighthembodiment. However, in the present embodiment, since the electrodeportion 3 a of the common electrode is constituted by the transparentelectric conductor, slight increase in the line width thereof will notsubstantially decrease the aperture ratio. Accordingly, in the casewhere the effect of improving the luminance by recycled light cannot beobtained much, it is preferable that the pixel electrode 4 constitutedby the non-transparent electric conductor should be downsized as much aspossible, and the line width of the electrode portion 3 a of the commonelectrode should be widened.

Furthermore, similarly to the eighth embodiment, when the scanningsignal line 6 and the common electrode 3 are formed in the same layer, adistance between the electrode portion 3 a of the common electrode andthe scanning signal line 6 becomes 3-6 μm. Since they are formed veryclose to each other, there have been a high probability that a faultoccurs due to short-circuit. However, in the present embodiment, theelectrode portion 3 a of the common electrode is formed in a layerseparated by first and second insulating layers from a layer in whichthe scanning signal line 6 is formed, thereby eliminating the fault dueto short-circuit.

While, in the above description, only the electrode portion 3 a of thecommon electrode is constituted by the transparent electric conductor,the electrode portion 4 a of the pixel electrode 4 may be constituted bythe transparent electric conductor. In this case, a wiring portion ofthe pixel electrode is formed in the same layer that the pixel electrode4 is formed in the case described above, and the electrode portion ofthe pixel electrode is formed in the same layer that the electrodeportion 3 a of the common electrode 3 is formed in the case describedabove. It should be note that both of the electrode portions of thecommon electrode and the pixel electrode may be constituted by thetransparent electric conductor.

Furthermore, in the present embodiment, the semiconductor switchingdevice 7 is constituted by the channel etching type TFT. Since thesecond insulating layer also plays a role as a protection layer,employing the channel etching type TFT in the liquid crystal display inwhich the electrode portions of the electrodes are constituted by thetransparent electric conductor provides optimum constitution withrespect to the process.

TENTH EMBODIMENT

A tenth embodiment of the present invention exemplifies a liquid crystaldisplay constituted such that in-panel liquid crystal operation circuitcomponents are constituted by a plurality of layers having differentreflectance, an array substrate side layer has a high reflectance, and aliquid crystal side layer has a low reflectance.

FIG. 18 is a view showing a constitution of a portion of a pixel portionof a liquid crystal display according to a tenth embodiment of thepresent invention. In FIG. 18, the same reference numerals as in FIG. 13b denote the same or corresponding elements. A constitution in thevicinity of the pixel of the liquid crystal display according to thepresent embodiment, when seen in a plan view, is identical to the liquidcrystal display 100 of the eighth embodiment, that is, the constitutionshown in FIG. 13 a. FIG. 18 is a sectional view taken in the directionof arrows substantially along line XIIIb-XIIIb of FIG. 13 a.

In FIG. 18, the electrode portion 3 a of the common electrode 3 has atwo-layer structure constituted by a high reflectance layer 3 a′ formedin the array substrate 1A side and a low reflectance layer 3 a″ formedin the liquid crystal 2 side. Furthermore, the electrode portion 4 a ofthe pixel electrode 4 has a two-layer structure constituted by a highreflectance layer 4 a′ formed in the array substrate 1A side and a lowreflectance layer 4 a″ formed in the liquid crystal 2 side. The highreflectance layers 3 a′, 4 a′ of the electrode portions 3 a, 4 a of bothelectrodes 3, 4 are made of metallic material having a high reflectance,and the low reflectance layers 3 a″, 4 a″ are made of, for example,Cr-based metallic material having a reflectance of approximately 60%.Other in-panel liquid crystal operation circuit components that are notshown, that is, a wiring portion of the common electrode, a wiringportion of the pixel electrode, the video signal line, the scanningline, and a wiring portion of the semiconductor switching device alsohave the same two-layer structures as described above.

Function and effects of the liquid crystal display thus constituted willbe described. If all of the in-panel liquid crystal operation circuitcomponents are constituted by the high reflectance electric conductorsimilarly to the eighth embodiment, a reflected light due to an ambientlight such as room light, that is, an undesired light is increased, andthe amount of light in dark display is increased, thereby causing thecontrast to be decreased. Therefore, formation of a low reflectancelayer in a side of the in-panel liquid crystal operation circuitcomponents where the liquid crystal panel 101 is seen, that is, in theopposing substrate 1B side enables a portion of the undesired light tobe absorbed, thereby suppressing decrease in the contrast due to theundesired light.

It should be noted that in the case where the high reflectance layer isconstituted by the high reflectance electric conductor, a thicknessthereof may be any thickness which can reflect a light satisfactorilybut not necessarily determined based on an electric resistance thereof.For example, 2000 angstrom or more may be suitable.

Furthermore, the low reflectance layer is not necessarily constituted bythe electric conductor; the low reflectance layer may be made ofnon-conductive material having a low reflectance.

Furthermore, while, in the above description, the in-panel liquidcrystal operation circuit components are of two-layer structure, thein-panel liquid crystal operation circuit components may be constitutedby 3 or more layers. For example, a structure in which an ordinaryconductive layer is retained between a low reflectance layer and a highreflectance layer may be suitable.

ELEVENTH EMBODIMENT

FIGS. 19 a and 19 b are views showing a constitution in the vicinity ofa pixel portion of a liquid crystal display according to an eleventhembodiment of the present invention, wherein FIG. 19 a is a plan view,and FIG. 19 b is a sectional view taken in the direction of arrowssubstantially along line XIXb-XIXb of FIG. 19 a. In FIGS. 19 a and 19 b,the same reference numerals as in FIG. 16 denote the same orcorresponding elements.

As shown in FIGS. 19 a and 19 b, differently from the ninth embodiment,a light-blocking layer 13 is provided on the array substrate 1A in thepresent embodiment. The light-blocking layer 13 is formed between thesecond insulting layer 11 and the alignment layer 9A so as to bepositioned above the video signal line 5 and have a wider width than thevideo signal line 5. Accordingly, the light-blocking layer 13 is formedto be stripe-shaped in the present embodiment. The other respects aresimilar to those of the ninth embodiment. Reference numeral 14 denotesthe first insulating layer not shown in FIG. 16. Furthermore, althoughnot shown in FIG. 16, the contact hole 11 a is filled with an electricconductor. In this constitution, since the light-blocking layer 13 isformed on the array substrate 11A together with wiring of the videosignal line 5, the accuracy of positioning of the light-blocking layer13 is determined by the accuracy of printing at the time ofmanufacturing, thereby suppressing decrease in the aperture ratio due todisplacement in bonding the array substrate 1A and the opposingsubstrate 1B. Consequently, a liquid crystal panel having a highaperture ratio and a high luminance can be achieved.

TWELFTH EMBODIMENT

FIGS. 20 a and 20 b are views showing a constitution in the vicinity ofa pixel portion of a liquid crystal display according to an twelfthembodiment of the present invention, wherein FIG. 20 a is a plan view,and FIG. 20 b is a sectional view taken in the direction of arrowssubstantially along line XXb-XXb of FIG. 20 a. In FIGS. 20 a and 20 b,the same reference numerals as in FIG. 13 denote the same orcorresponding elements.

As shown in FIGS. 20 a and 20 b, differently from the eighth embodiment,the common electrode 3 is constituted by a so-called multi-layer commonelectrode, and the video signal line 5 is constituted by a so-calledmulti-layer video signal line. That is, the common electrode 3 includesan electrode portion 3 c′ located in a pixel 103 similar to the eighthembodiment and, in addition thereto, an electrode portion 3 c″ locatedabove the video signal line 5, that is, above a borderline of the pixel103, and these electrode portions 3 c′, 3 c″ are connected by a wiringportion 3 b. Describing more in detail, an electrode portion 4 a andwiring portions 4 b′, 4 b″ of the pixel electrode 4 and the video signalline 5 are formed on an upper surface of the array substrate 1A, aninsulating layer 11 is formed thereon, and the electrode portions 3 c′,3 c″ of the common electrode 3 are formed on the insulating layer 11.The electrode portions 3 c′, 3 c″ of the common electrode 3 and theelectrode portion 4 a of the pixel electrode 4 are formed so as toextend linearly in an extending direction of the video signal line 5.Furthermore, the electrode portion 3 c″ located above the vide signalline 5 of the common electrode 3 is formed so as to have a slightlywider width than the video signal line 5. The other respects are similarto those of the eighth embodiment.

In this constitution, since a transversal electric field is formed asfar as an area close to the borderline of the pixel 103, a substantialaperture ratio of the array substrate can be increased. Consequently, aliquid crystal display having a high luminance can be obtained.

THIRTEENTH EMBODIMENT

FIG. 21 is a plan-view showing a constitution in the vicinity of a pixelportion of a liquid crystal display according to a thirteenth embodimentof the present invention. In FIG. 21, the same reference numerals as inFIG. 19 denote the same or corresponding elements.

As shown in FIG. 21, differently from the eleventh embodiment, in thepresent embodiment, the video signal line 5 and the light-blocking layer13 are formed so as to be bent in a zigzag and extend conforming inshape to respective electrode portions 3 a, 4 a ofsideways-pointing-shaped common and pixel electrodes 3, 4 in a directionperpendicular to an extending direction of the scanning signal line 6.The other respects are similar to those of the eleventh embodiment. Inthis constitution, increase in light-blocking area caused by bending theelectrode portion 3 a, 4 a of each electrode 3, 4 can be prevented.Consequently, a liquid crystal display having a high luminance can beobtained.

FOURTEENTH EMBODIMENT

FIGS. 22 a and 22 b are views showing a constitution in the vicinity ofa pixel portion of a liquid crystal display according to an fourteenthembodiment of the present invention, wherein FIG. 22 a is a plan view,and FIG. 22 b is a sectional view taken in the direction of arrowssubstantially along line XXIIb-XXIIb of FIG. 22 a. In FIGS. 20 a and 20b, the same reference numerals as in FIG. 16 denote the same orcorresponding elements.

As shown in FIGS. 22 a and 22 b, differently from the ninth embodiment,the light-blocking layer 13 and a color filter 8 are formed on the arraysubstrate 1A in the present embodiment. The other respects are similarto those of the ninth embodiment. In this constitution, since thelight-blocking layer 13 and the color filter 8 are formed on the arraysubstrate 1A together with wirings of the video signal line 5, thescanning signal line 6, and the like, accuracy of positioning of thelight-blocking layer 13 and the color filter 8 is determined by accuracyof printing at the time of manufacturing, thereby suppressing decreasein an aperture ratio due to displacement in bonding the array substrate1A and the opposing substrate 1B. Consequently, a liquid crystal panelhaving a high aperture ratio and a high luminance can be achieved.

FIFTEENTH EMBODIMENT

A fifteenth embodiment of the present invention is a combination of thefirst embodiment and the tenth embodiment.

FIG. 23 is a sectional view schematically showing a constitution of aliquid crystal display according to the present embodiment. In FIG. 23,the same reference numerals as in FIG. 12 denote the same orcorresponding elements.

As shown in FIG. 23, in the liquid crystal display according to thepresent embodiment, in-panel liquid crystal operation circuit components381 formed on an inner face of the array substrate 1A is constituted bya transparent layer 381A formed on the array substrate 1A and anon-transparent layer 381B, 381C formed thereon and having a narrowerwidth than it. Then, the non-transparent layer 381B, 381C includes aplurality of layers (two layers, herein), a layer closest to the arraysubstrate 1A is made of material having a highest reflectance, a layer381C closest to the liquid crystal layer is made of material having alowest reflectance, and a blackening process is performed on a surfacethereof (380D). The transparent layer is made of, for example, ITO.Furthermore, the layer 381B is made of, for example, silver Ag-basedalloy, and the layer 381C is made of, for, example, chromium Cr-basedalloy. Also, a blackening process of the layer 381C is performed by, forexample, providing a low reflectance chromium layer 381D thereon, orperforming plasma-treatment after providing silver Ag-based materialthereon.

In this constitution, similarly to the first embodiment, the contrastand the luminance are improved because of the two-layer structures ofthe transparent layer 381A and the non-transparent layer 381B, 381C.Furthermore, even when an ambient light 802 is incident from theopposing substrate 1B on the in-panel liquid crystal operation circuitcomponents 381, since a surface thereof is blackened, reflection isprevented. Consequently, the contrast of the display screen is improved.

Furthermore, for the purpose of simplification, the blackening process(381D) may be omitted. Even in this case, improvement in the contrastcan be obtained because of the reduction of undesired light.

SIXTEENTH EMBODIMENT

FIG. 24 is a sectional view schematically showing a constitution of aliquid crystal display according to a sixteenth embodiment of thepresent invention. In FIG. 24, the same reference numerals as in FIG. 12denote the same or corresponding elements.

As shown in FIG. 24, in the present embodiment, a high reflectance layer371′ is formed below in-panel liquid crystal operation circuitcomponents 371 formed on the array substrate 1A with an insulating layer372 interposed therebetween. The high reflectance layer 371′ is made of,for example, silver Ag-based material and formed so as to overlap withthe in-panel liquid crystal operation circuit components 371 when seenin a direction-perpendicular to the liquid crystal panel 101.

In this constitution, the amount of recycled light is increased, and theluminance of the display screen is improved. It should be noted thatthis constitution could be similarly applied to non-transparent wiringssuch as scanning signal line, video signal line and the like formed onan array substrate of a TN-mode liquid crystal display.

In the first to seventh embodiments, the two-layer structure including alayer constituted by a transparent body (a transparent electricconductor or a transparent dielectric substance) and a layer constitutedby a non-transparent body (a non-transparent electric conductor or anon-transparent dielectric substance) in the structure formed in thepixel may be formed by forming a layer constituted by a transparent bodyand then a layer constituted by a non-transparent body having a narrowerwidth than the layer constituted by a transparent body. Furthermore,such a structure constituted by a non-transparent portion and atransparent portion may be such that, when seen in a directionperpendicular to the liquid crystal panel, an edge thereof isconstituted by a transparent body, and a central portion thereof isconstituted by a non-transparent body, and therefore may be structuredsuch that an island-shaped non-transparent portion is surrounded by anannular transparent portion, rather than the two-layer structure.

In the eighth to eleventh and fourteenth embodiments, the electrodeportions may be of other shape than bent-shape, that is, oflinear-shape, enclosure-shape, and the like. In either shape, an effectof substantially increasing the aperture ratio can be obtained.

In the first to fifteenth and eighth to fourteenth embodiments, whilethe case where the semiconductor switching device was constituted by thechannel etching type TFT was described, the semiconductor switchingdevice may be constituted by a channel protection-type TFT or any othertype of semiconductor switching device.

In the eighth to fourteenth embodiments, if the semiconductor switchingdevices are constituted by an active semiconductor layer made of p-Si(polysilicon), the semiconductor switching device can be downsized.Specifically, for example, in the TFT 160 shown in FIG. 1 b, a channelportion can be constituted by a polysilicon p-si layer in place of theamorphous silicon a-si layer 162, and the source area and drain area canbe constituted by N-type polysilicon n⁺p-Si layer in place of N-typeamorphous silicon n⁺a-Si layer 163. While, the above embodiments, FIGS.13, 16, 19, 20, 21 illustrate the semiconductor switching device 7 asbeing placed in the area above the scanning signal line 6, thesemiconductor switching device actually runs over the area of the pixel103. Therefore, downsizing of the semiconductor switching device 7enables the aperture ratio of the array substrate 1A to be increased.Consequently, a liquid crystal display having a high luminance can beobtained.

In the first to fourteenth embodiments, the backlight was used as alight source. Alternatively, only a reflecting plate may be provided,and a reflected light obtained in such a way that an ambient light fromthe opposing substrate side is reflected on the reflecting plate may beused as a light source.

Numerous modifications and alternative embodiments of the invention willbe apparent to those skilled in the art in view of the foregoingdescription. Accordingly, the description is to be construed asillustrative only, and is provided for the purpose of teaching thoseskilled in the art the best mode of carrying out the invention. Thedetails of the structure and/or function may be varied substantiallywithout departing from the spirit of the invention.

1. A liquid crystal display comprising: a liquid crystal panel includingan array substrate having an upper surface on which a common electrode,a pixel electrode, a scanning signal line, a video signal line, and asemiconductor switching device are formed, an opposing substratedisposed so as to be opposite to the upper surface of the arraysubstrate, and a liquid crystal layer disposed between the arraysubstrate and the opposing substrate, and a reflecting face formed belowthe liquid crystal panel, wherein a light reflected on the reflectingface is transmitted through the liquid crystal panel, and wherein atleast one electrode of the common electrode and the pixel electrode isconstituted by an electrode portion and a wiring portion, the electrodeportion is at least partially constituted by a transparent electricconductor, the electrode portion is formed in a layer separated by aninsulating layer from a layer in which the scanning signal line isformed, and the wiring portion is formed in the layer in which thescanning signal line is formed.
 2. The liquid crystal display accordingto claim 1, wherein the common electrode and the pixel electrode areboth constituted by a wiring portion and a comb-shaped electrodeportion, and a width of the electrode portion at least partiallyconstituted by a transparent electric conductor is different from awidth of a part of the electrode portion which is not constituted by atransparent electric conductor.
 3. The liquid crystal display accordingto claim 2, wherein the width of the electrode portion partiallyconstituted by a transparent electric conductor is larger than the widthof the part of the electrode portion which is not constituted by atransparent electric conductor.
 4. The liquid crystal display accordingto claim 2, wherein a width of each electrode portion of the commonelectrode and the pixel electrode is 1 μm or more and 10 μm or less. 5.The liquid crystal display according to claim 1, wherein the commonelectrode and the pixel electrode are both constituted by a wiringportion and a comb-shaped electrode portion, and widths of both of theelectrode portions of the common electrode and the pixel electrode arestructured for liquid crystal molecules disposed above the electrodeportion partially constituted by a transparent electric conductor to bemodulated by an electric field generated between the electrode portionof the common electrode and the electrode portion of the pixelelectrode.
 6. The liquid crystal display according to claim 5, whereinat least one of the width of each electrode portion of the commonelectrode and the pixel electrode, and a spacing between the electrodeportions of the common electrode and the pixel electrode issubstantially equal to or smaller than a spacing between the arraysubstrate and the opposing substrate.